Sensing technology using a smell (gas) sensor is widely used for odor determination, measurement of volatile organic compounds (VOC) in the atmosphere, performance confirmation of air cleaners, trouble detection of devices, and so on because it is capable of digitizing smell in the air.
As a conventional gas sensing method, there are devices such as a flame ionization detector (FID), a photo-ionization detector (PID), and a non-dispersive infra-red (NDIR) gas analyzer. These devices have problems regarding portability, risk due to the use of a flammable gas, life and price of a light source used for the measurement, substance recognition performance, and so on. Therefore, the development of a small sensor advantageous in the assembly in a processing device and the measurement at a work site has been in progress.
As a semiconductor gas sensor which is a small sensor, there has been proposed a sensor that is capable of measuring gas concentration by using a change that electrical properties such as electrical resistance undergo when oxygen adsorbed on porous tin oxide (SnO2) is consumed by a reducing substance. However, a conventionally used oxide semiconductor sensor has several problems regarding detection sensitivity, an operating temperature (300 to 500° C.), durability, gas selectivity, and so on.